A Zeiss LSM 510 confocal microscope is requested to replace the current but obsolete MRC 600 confocal microscope in the W. M. Keck Imaging Facility at the Whitehead Institute. This system was chosen after on-site evaluation by users of demo systems by Zeiss, BioRad, and Leica. As part of the shared instrumentation in the Imaging Facility, the Zeiss confocal will directly support the NIH-supported research of eight labs in the WI and MIT. In additional other NIH-supported groups will have access to the new system. The confocal microscope consists of a Zeiss Axiovert microscope equipped with fluorescence and DIC optics, an integrated scanning unit coupled to three laser illuminators, and a Pentium PC that controls the operation of the microscope, image acquisition, and image processing with a Windows NT-based software. At a later time, the system will be up-graded to multiphoton optics using WI funds. The Whitehead Institute commits $100,000 to defray the purchase price. The maintenance and user support costs are covered by a WI budget.